The first thermally stable half-sandwich titanium zwitterionic complex

Article abstract of DOI:10.1016/j.jorganchem.2007.01.022

Thermally stable zwitterionic complex [(η⁵-C₅Me₅)Ti(Ot-Bu)₂]^(δ+)[(μ-Me)B(C₆F₅)₃]^(δ-) (5) was formed by mixing equimolar quantities of [(η⁵-C

Full text of DOI:10.1016/j.jorganchem.2007.01.022

Journal of Organometallic Chemistry 692 (2007) 2064–2070
www.elsevier.com/locate/jorganchem
The first thermally stable half-sandwich titanium zwitterionic complex
a
b
c
a
´
´ ˇ
´
ˇ´
ˇ
Jirˇı Pinkas , Vojtech Varga , Ivana Cısarova , Jirı Kubista ,
a
a,
*
´
Michal Horacˇek , Karel Mach
a
J. Heyrovsky´ Institute of Physical Chemistry of Academy of Sciences of the Czech Republic, v.v.i., Dolejsˇkova 3, 182 23 Prague 8, Czech Republic
b
´
Research Institute of Inorganic Chemistry, Revolucˇnı´ 84, 400 01 Ustı´ nad Labem, Czech Republic
Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
c
Received 31 October 2006; received in revised form 12 January 2007; accepted 16 January 2007
Available online 23 January 2007
Abstract
Thermally stable zwitterionic complex [(g5-C5Me5)Ti(Ot-Bu)2](d+)[(l-Me)B(C6F5)3](dꢀ) (5) was formed by mixing equimolar quanti-
ties of [(g5-C5Me5)TiMe(Ot-Bu)2] and [B(C6F5)3]. The compound was recrystallized from hot toluene and has been stable so far for 1
1
year at ambient temperature in the solid state and in toluene solution. The H, 19F and 1D NOESY NMR spectra in C6D6 solution
proved the inner sphere ion pair structure of 5. The X-ray crystal structure of 5 revealed that the bridging methyl group is r-bonded
to boron, and all its C–H bonds fulfil criteria for agostic bonding interaction with the titanium atom. In contrast to the stable solution
in C6D6 compound 5 decomposed in CD2Cl2 solvent within hours at room temperature.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Half-sandwich titanocenes; Zwitterionic complex; NMR spectra; Crystal structure
1. Introduction
merization on ion-pair single-site catalysts, the polymeriza-
tion to a-PS proceeding in polar solvents like CH2Cl2 or
1,2-C2H4Cl2 pointed to a free carbocationic catalysis. This
suggestion was corroborated by easy polymerization of
a-methylstyrene [3b], vinyl ethers [3c], N-vinylcarbazole
or isobutene [3d], the monomers which are known to
polymerize under action of carbocationic initiators [3e].
The high activity of the single-site systems was, however,
conditioned by the presence of the monomer when the cat-
alyst components were reacting. Mixing of the catalyst
components in the absence of olefins resulted in negligible
polymerization activity. Indeed, NMR tube experiments
with mixing the components at low temperature gave
evidence for the formation of the [(g5-C5Me5)TiMe2]+
[MeB(C6F5)3]ꢀ complex and its rapid decomposition at
room temperature [4]. Modification of the titanium compo-
nent by introduction of an alkoxy or aryloxy group instead
of one or two methyls gave generally less active catalysts
because of decreased electrophilicity of the metal due
to a p-electron donation of the alkoxy oxygen lone electron
pairs to the empty d-orbitals [5a]. An attempt to suppress
this p-electron donation by using perfluoroaryl or
Various half-sandwich titanium trihalides have been
used in combination with methylalumoxane (MAO) as cat-
alysts for effective polymerization of styrene to syndiotactic
polystyrene (syn-PS), however, the molecular structure of
catalysts is difficult to investigate [1]. Successful investiga-
tions of single site polymerization catalysts based on early
transition metal metallocene dialkyls/tris(pentafluorophe-
nyl)borane [2] raised the wave of interest in analogous
half-sandwich catalysts. The catalysts formed from [(g5-
C5Me5)TiMe3] and [B(C6F5)3], where the formation of an
ion pair [(g5-C5Me5)TiMe2]+[MeB(C6F5)3]ꢀ was antici-
pated, appeared to be highly active for polymerization of
ethene to a high-molecular polymer, and styrene to syn-
PS or atactic polystyrene (a-PS) in dependence on the
solvent nature [3a]. Whereas the formation of syn-PS in
aromatic solvents was compatible with stereodirected poly-
*
Corresponding author. Tel.: +420 (2) 6605 3735; fax: +420 (2) 8658
2307.
E-mail address: mach@jh-inst.cas.cz (K. Mach).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.01.022

J. Pinkas et al. / Journal of Organometallic Chemistry 692 (2007) 2064–2070
2065
Scheme 2. Synthesis of half-sandwich titanium(IV) complexes 1–4.
Scheme 1. Decomposition pathways for half-sandwich aryloxo zwitter-
ionic complexes (taken from Ref. [6]).
[(g5-C5Me5)TiCl(Ot-Bu)2] (1) or solid [(g5-C5Me5)Ti-
Cl2(Ot-Bu)] (2) which were purified by vacuum distillation
and crystallization from hexane, respectively. Compounds
1 and 2 were reacted with one or two equivalents of LiMe
in toluene, respectively, to give yellowish oils of 3 and 4. Both
the compounds were purified by vacuum distillation, and
characterized by 1H and 13C NMR and IR spectra.
perfluoroaryloxy ligands resulted in identification of cat-
ionic complexes [(g5-C5Me5)TiMeR]+ [MeB(C6F5)3]ꢀ
where R = C6F5 or OC6F5 at low temperature by NMR
spectra. Unfortunately, the complexes could not be isolated
because of their low thermal stability. The compound made
from [(g5-C5Me5)TiMe(OC6F5)2] at ꢀ50 ꢁC in CD2Cl2 was
according to NMR spectra the ion pair [(g5-C5Me5)-
Ti(OC6F5)2]+ [MeB(C6F5)3]ꢀ showing a free borate anion.
Unfortunately, the compound dissociated at only ꢀ10 ꢁC
to initial components [5b]. A number of compounds [(g5-
C5H5)TiMe2OR] where R is the phenyl group 2,6-disubsti-
tuted with bulky substituents (like phenyl, 1-naphthyl,
t-Bu, i-Pr, Me) were used for the formation of cationic
complexes with [B(C6F5)3]. The NMR spectra gave evi-
dence for the presence of ion-pair dissociation and the
Ti–Me/Ti–Me–B exchange process, both at low tempera-
tures. At ambient temperature, two decomposition pro-
cesses of the cationic complex were recognized depending
on the nature of substituents at the aryloxy ligand. In
one, elimination of methane afforded neutral [(g5-
C5H5)Ti(OAr)(C6F5){CH2B(C6F5)2}], in the other elimina-
tion of bis(pentafluorophenyl)methylboron gave [(g5-
C5H5)TiMe(OAr)(C6F5)] (Scheme 1) [6]. Another catalyst
precursor, the trialkylsiloxy complex [(g5-C5Me5)TiMe2O-
SiR3], where R = 2-(diphenylmethylsilyl)ethane-1-yl, gave
rise to the cationic complex which had the half-life time
of 2 days, and decomposed in C6D6 via both ways of
Scheme 1 simultaneously [7].
Addition of one equivalent of [B(C6F5)3] to 3 in toluene
resulted in the formation of new zwitterionic complex [(g5-
C5Me5)Ti(Ot-Bu)2][(l-Me)B(C6F5)3] (5) as virtually the
only product (Scheme 3). The thermally robust 5 was
recrystallized from hot toluene to give orange plate crystals
suitable for X-ray single crystal structure analysis (see
below). Its stability in solution, however, strongly
depended upon the solvent nature. Whereas in C6D6 or tol-
uene it remained stable for so far one year, in CD2Cl2 it
1
decomposed within hours at room temperature. The H
NMR spectrum of 5 in C6D6 displayed in addition to sig-
nals belonging to C5Me5 and OCMe3 at 1.63 and 1.01,
respectively, a broad signal at 0.45 ppm with halfwidth
about 20 Hz. A remarkable high-field chemical shift of this
signal in comparison with the unassociated [MeB(C6F5)3]ꢀ
anion in aromatic solvents (1.2–1.4 ppm) [8] indicates that
compound 5 forms a contact ion-pair containing bridging
Tiꢁ ꢁ ꢁMe–B moiety. In order to support this suggestion
Here we report the synthesis of half-sandwich complexes
[(g5-C5Me5)TiMe(Ot-Bu)2] (3) and [(g5-C5Me5)TiMe2(Ot-
Bu)] (4), and the formation of thermally stable cationic
complex [(g5-C5Me5)Ti(Ot-Bu)2][(l-Me)B(C6F5)3] (5) from
3 and [B(C6F5)3].
2. Results and discussion
The precursors for the formation of cationic complexes
[(g5-C5Me5)TiMe(Ot-Bu)2] (3) and [(g5-C5Me5)TiMe2(Ot-
Bu)] (4) were obtained from commercial [(g5-C5Me5)TiCl3]
in two steps according to Scheme 2. Addition of stoichiome-
tric amounts of Li(Ot-Bu) in hexane afforded oily
Scheme 3. Formation of complexes 5 and 6.

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J. Pinkas et al. / Journal of Organometallic Chemistry 692 (2007) 2064–2070
1D NOESY experiments were carried out with irradiation
of C5Me5 or OCMe3 protons. The both of them showed a
close through space interaction with the MeB group. More-
over, the 19F NMR spectrum of 5 displayed the difference
between the meta and para fluorine resonances Dd(m,p-
F) = 5.0 ppm, the value indicative for a strong cation–
anion association [8a]. All these features allow us to assign
5 to an inner sphere ion pair (ISIP) [8d].
C10
H3
C1
C5
C2
C3
F5
C4
C12
1
Ti
H1
The fresh CD2Cl2 solution of 5 showed the similar H
NMR spectrum with downfield shifted C5Me5 and OCMe3
signals at 2.13 and 1.35 ppm, respectively, and slightly
upfield shifted MeB resonance at 0.39 ppm. Within an
hour, however, a new set of resonances at 2.19, 1.41, and
0.41 ppm arose changing into a tangle of signals after sev-
eral days. It can be suggested that the new set of distinct
signals belonged to aggregated polynuclear species which
were proposed to facilitate undesired side reactions [9].
The formation of polynuclear species was apparently due
to an easier ion-pair separation in the more polar CD2Cl2
solvent [10].
C11
O1
C24
B
C18
H2
C30
O2
C34
Fig. 1. The PLATON drawing of 5 (30% probability ellipsoids) with atom
labeling scheme. Hydrogen atoms except those residing on the bridging
C(11) atom are omitted for clarity.
The EI-MS spectrum of 5 occurred only at 280 ꢁC show-
ing free [B(C6F5)3] and the C5Me5 ion and their fragment
ions. The infrared spectrum of 5 confirmed the presence
of both titanium and boron components, however, it is
too complex to identify features belonging to the bridging
Tiꢁ ꢁ ꢁMe–B group. Thus, the most valuable information
on the structure of 5 was obtained from X-ray single crystal
analysis (see below). Compound 5 in saturated toluene
solution did not catalyze the polymerization of ethene at
atmospheric pressure.
ligand, two tert-butoxy groups and by l-Me group binding
together the anionic [MeB(C6F5)3]dꢀ and the [(g5-
C5Me5)Ti(Ot-Bu)2]d+ moieties. There is no apparent steri-
cal crowding imposed by the ligands. The distance of the
least-squares plane of the cyclopentadienyl ring to the tita-
˚
nium atom (2.0445(7) A) is within two esd’s equal to the
Ti–Cg (Cg is the centroid of the cyclopentadienyl ring) dis-
˚
tance, and the maximum deviation of 0.160(3) A for the
methyl carbon atom C(10) from the above plane opposite
to titanium falls into the values found in not crowded
half-sandwich ½ðg5-C5Me4t-BuÞTiCl3ꢂ or ½fðg5-C5Me4t-
BuÞTiCl2g2Oꢂ complexes [12]. Likewise, the C–C bonds in
tert-butoxy groups as well as the C–F bonds in the C6F5
Mixing of equimolar quantities of 3 with [Ph3C]
[B(C6F5)4] in toluene at ambient temperature did not afford
any isolable product due to decomposition of the expected
solvent-separated
ion
pair
[(g5-C5Me5)Ti(Ot-Bu)2]
[B(C6F5)4] (6). The latter was observed when the above
components were mixed in CD2Cl2 at ꢀ50 ꢁC (Scheme 3).
1H NMR spectrum of 6 displayed the C5Me5 and OCMe3
signals at 2.06 and 1.35 ppm, respectively, only slightly
downfield shifted from resonances of 3. The 19F NMR
spectrum showed Dd(m,p-F) = 3.9 ppm, typical for the
uncoordinated [B(C6F5)4]ꢀ anion [11].
Table 1
˚
Selected bond lengths (A) and bond angles (ꢁ) for compound 5
Ti–Cga
Ti–C(2)
2.0464(7)
2.332(1)
Ti–C(1)
Ti–C(3)
2.387(1)
2.350(1)
Ti–C(4)
2.390(1)
Ti–C(5)
2.421(1)
Addition of one equivalent of [B(C6F5)3] to 4 in hexane
solutions at ambient temperature led to an extensive gas
evolution, and NMR spectra of the resulting product in
C6D6 indicated a complete loss of tert-butoxyl groups.
Recently, elimination of isobutene from the [Cp2Zr(Ot-
Bu)]+ cation resulting in the formation of poly(isobutene)
Ti–O(1)
1.766(1)
2.436(1)
1.412–1.427(2)
1.655(2)
1.655(2)
Ti–O(2)
1.756(1)
1.679(2)
1.497–1.504(2)
1.649(2)
1.438(1)
Ti–C(11)
Cring–Cring(Cp)
B–C(12)
B–C(24)
O(2)–C(34)
C–CMe(Ot-Bu)
B–C(11)
Cring–CMe
B–C(18)
O(1)–C(30)
C–F(range)b
C–C(Ph)b
1.441(1)
1.503–1.523(3)
1.339–1.358(2)
1.368–1.393(3)
2þ
and ½Cp2Zrðl-OHÞꢂ2 has been well-evidenced by NMR
Cg–Ti–O(1)
Cg–Ti–C(11)
O(1)–Ti–C(11)
Ti–O(1)–C(30)
Ti–C(11)–B
C(11)–B–C(18)
C(12)–B–C(24)
C(18)–B–C(24)
B–C(11)–H(2)
a
118.26(4)
113.98(4)
97.64(5)
166.1(1)
169.0(1)
112.3(1)
113.2(1)
113.6(1)
105(1)
Cg–Ti–O(2)
119.61(4)
106.80(6)
96.35(5)
169.9(1)
112.9(1)
100.9(1)
104.3(1)
113(1)
spectra and X-ray crystallography [11]. In the present sys-
tem a mixture of titanium products was generated where
individual components were not identified.
O(1)–Ti–O(2)
O(2)–Ti–C(11)
Ti–O(2)–C(34)
C(11)–B–C(12)
C(11)–B–C(24)
C(12)–B–C(18)
B–C(11)–H(1)
B–C(11)–H(3)
2.1. X-ray crystal structure of 5
105(1)
The PLATON drawing of 5 is shown in Fig. 1, and important
molecular parameters are listed in Table 1. The titanium
atom is pseudotetrahedrally coordinated by the g5-C5Me5
Cg denotes the centroid of C(1–5) cyclopentadienyl ring.
Range of values for all the three C6F5 groups.
b

J. Pinkas et al. / Journal of Organometallic Chemistry 692 (2007) 2064–2070
2067
groups fall into narrow distance ranges (Table 1), not indi-
cating a steric crowding. The tert-butoxytitanium moieties
are bent at the oxygen atom comparably to [(g5-C5HMe4)2-
Ti(Ot-Bu)] [13] or [{Ti(Ot-Bu)3}{Co(CO)3}] [14], and the
Ti–O bond lengths (Table 1) are shorter with respect to that
methyl group does not allow us to determine the 1JCH cou-
pling constants whose reduced value would be indicative
for the presence of agostic interaction [17a,20]. The crystal
structure determination of 5 confirmed the Tiꢁ ꢁ ꢁMe–B
bridging moiety, which is analogous to that found in zirc-
onocene cationic complexes [9,19]. The position of bridging
methyl group with respect to the titanium atom allows us
to consider a remarkable agostic bonding contribution to
a generally accepted electrostatic bonding attraction. The
cationic moiety is apparently unstable in solvent-separated
ion pair as observed for 5 in polar CD2Cl2 solvent or for 6
containing the [B(C6F5)4]ꢀ anion.
˚
in the former (1.8425(14) A) and longer with respect to
˚
those in the latter compound (1.738(9)–1.743(5) A). The tet-
rahedral coordination about the boron atom is also dis-
torted showing the angles C(11)–B–C(24) and C(12)–B–
C(18) smaller than the other boron-centered angles (Table
1). The B–C(11) bond length is only slightly longer than
the B–Cipso bond lengths, and B–C(11)–H angles clearly
indicate that the methyl group is regularly r-bonded to
the boron atom. A larger value of the B–C(11)–H(1) angle
(113(1)ꢁ) against the other two hydrogen-containing angles
of 105(1)ꢁ and 105(1)ꢁ is connected with the bent bridging
links (Ti–C(11)–B 169.0(1)ꢁ). Accordingly, the Ti–H(1) dis-
3. Experimental
3.1. Chemicals and methods
˚
tance of 2.42(2) A is longer than the Ti–H(2) and Ti–H(3)
All reactions with moisture and air-sensitive compounds
were carried out under argon or on a high-vacuum line using
all-sealed glass devices equipped with breakable seals. Li(Ot-
Bu) (1.0 M solution in hexane), LiMe (1.6 M solution in
diethylether) and LiAlH4 were obtained from Aldrich and
used as received. [B(C6F5)3], [(g5-C5Me5)TiCl3] and
[Ph3C][B(C6F5)4] were purchased from Strem, and the for-
mer two purified by crystallization from hexane. Solvents
tetrahydrofuran (THF), hexane, and toluene were dried by
refluxing over LiAlH4 and stored as solutions of dimeric
titanocene [(l-g5:g5-C10H8)(l-H)2{Ti(g5-C5H5)}2] [21].
1H (299.98 MHz), 13C (75.44 MHz) and 19F (282.22 MHz)
NMR spectra were recorded on a Varian Mercury 300 spec-
trometer at 298 K if not noticed otherwise. Chemical shifts
(d/ppm) are given relative to the solvent signal (C6D6: dH
7.15, dC 128.00; CD2Cl2: dH 5.32, dC 54.00). EI-MS spectra
of 5 were measured on a VG-7070E mass spectrometer at
70 eV. Crystalline samples in sealed capillaries were opened
and inserted into the direct inlet under argon. The spectra are
represented by the peaks of relative abundance higher than
7% and by important peaks of lower intensity. Infrared spec-
tra of hexane solutions of 1–4 under argon in KBr cuvettes
were measured on a Magna 550 Nicolet spectrometer in
the range 400–4000 cmꢀ1. KBr pellets of 5 were prepared
in a glovebox Labmaster 130 (mBraun) and then measured
in an air-protecting cuvette on a Nicolet Avatar FT IR spec-
˚
˚
distances of 2.28(2) A and 2.29(2) A, respectively. The Ti–
˚
C(11) distance of 2.436(1) A is longer than r–Ti–C bonds
in [(g5-C5Me5)2TiCH2CMe3] (2.231(5) A) [15] and a
˚
number of titanocene cyclopentadienyl ring-tethered titana-
˚
cyclopentanes (2.208(2)–2.270(5) A) [16], however, it
approaches the length of Ti–C(sp2) bonds to the g5-
C5Me5 ring in 5 (Table 1) and generally in all titanocene
compounds. Since the methyl C(11) atom has an sp3 hybrid-
ization its bonding to titanium has to be accomplished via
agostic bonding of its C–H bonds. All conditions for its
occurrence are fulfilled: the d0 titanium atom has empty
orbitals to interact with the r–C–H bonding orbital, the
Ti–C and Ti–H distances are comparable, and angles Ti–
C–H are smaller than 100ꢁ [17]. The agostic interaction with
one C–H bond on each of two vicinal methyl groups of the
decamethyltitanocene cation resulted in attraction of
both the methyl groups toward titanium so that
the agostic Ti–H/Ti–C distances were 2.16(3)
˚
˚
˚
˚
A/2.685(5) A and 2.20(3) A/2.652(4) A [18]. Compared to
the parameters for 5, the Ti–H distances are only slightly
shorter with respect to Ti–H(2) and Ti–H(3), and the Ti–
C distances considerably longer than Ti–C(11). A very
similar orientation of the bridging methyl group in
zirconocene contact ion pairs [Me4C2(g5-C5H4)2ZrMe]+
[MeB(C6F5)3]ꢀ [19a], rac-[Me2Si{g5-C5H2(2-Me-4-t-Bu)}2-
ZrMe]+[MeB(C6F5)3]ꢀ [19], and [{g5-C5H3(1,2-Me2)}2ZrMe]+
[MeB(C6F5)3]ꢀ [19b] was found, the Zr–C and Zr–H distances
to the bridging borate methyl being longer just due to a lar-
ger covalent radius of Zr with respect to Ti.
trometer in the range 400–4000 cmꢀ1
.
3.2. Synthesis of permethylcyclopentadienyl(chloro)titanium
tert-butanolates
2.2. Conclusions
Pentamethylcyclopentadienyl(chloro)titanium tert-butano-
lates were prepared by reacting [(g5-C5Me5)TiCl3] with one
or two equivalents of Li(Ot-Bu) [22].
High thermal stability of 5 probably results from a lower
Lewis acidity of the titanium atom induced by tert-butoxyl
ligands capable of back-donation of electron density.
Apparently for the same reasons compound 5 is catalyti-
3.2.1. [(g5-C5Me5)Ti(Ot-Bu)2Cl] (1)
Hexane solution of Li(Ot-Bu) (1.0 M, 17.4 ml,
17.4 mmol) was added dropwise within 2.5 h to a precooled
solution of [(g5-C5Me5)TiCl3] (2.51 g, 8.7 mmol) in 50 ml
of THF at ꢀ15 ꢁC. The reaction mixture was heated to
cally inactive for polymerization of ethene. The H, 19F
1
and 1D NOESY NMR spectra proved the ISIP structure
in C6D6 solution, however, a broad signal for the borate

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J. Pinkas et al. / Journal of Organometallic Chemistry 692 (2007) 2064–2070
room temperature, stirred for additional 3 h and then all
volatiles were evaporated in vacuum. A crude product
was extracted into hexane. Distillation of crude product
at 90 ꢁC/0.1 mm Hg gave compound 1 as a yellow oily
liquid. Yield 2.84 g (88%).
and purified by distillation at 70 ꢁC/0.1 mm Hg to give a
yellowish oily liquid of 4. Yield 1.79 g (84%).
1H NMR (C6D6): 0.40 (s, 6H, TiMe); 1.44 (s, 9H,
OCMe3); 1.83 (s, 15H, C5Me5). 13C {1H} NMR (C6D6):
11.72 (C5Me5); 32.37 (OCMe3); 47.81 (TiMe); 82.32
(OCMe3); 120.94 (C5Me5). IR (hexane solution, cmꢀ1):
1360 (s), 1232 (m), 1190 (vs), 1135 (w), 1111 (w), 1065
(w, sh), 1037 (vs), 904 (w), 883 (w), 795 (m), 758 (w), 694
(w), 625 (w, br), 550 (m), 520 (s), 462 (w), 414 (w).
1H NMR (C6D6): 1.31 (s, 18H, OCMe3); 2.03 (s, 15H,
C5Me5). 13C {1H} NMR (C6D6): 12.83 (C5Me5); 32.51
(OCMe3); 84.64 (OCMe3); 125.45 (C5Me5). IR (hexane
solution, cmꢀ1): 1358 (s), 1230 (m), 1188 (s), 1174 (s, sh),
1016 (vs), 993 (vs), 792 (m), 575 (m), 567 (m, sh), 567 (m,
sh), 482 (w), 472 (w), 429 (m), 403 (m).
3.4. Synthesis of [(g5-C5Me5)Ti(Ot-Bu)2][MeB(C6F5)3]
(5)
3.2.2. [(g5-C5Me5)Ti(Ot-Bu)Cl2] (2)
The above described procedure was used starting from
Li(Ot-Bu) solution (1.0 M, 8.4 ml, 8.4 mmol) and [(g5-
C5Me5)TiCl3] (2.43 g, 8.3 mmol). After workup, a crude
product was recrystallized from hexane to give analytically
pure 2 as orange crystals. Yield 2.21 g (82%).
A solution of 3 (0.40 g, 1.17 mmol) in 15 ml of toluene
was added to a solution of [B(C6F5)3] (0.60 g, 1.17 mmol)
in 20 ml of toluene. The reaction mixture was stirred for
2 h and then concentrated to cca. 20 ml. Heating of the
mixture to 60 ꢁC followed by slow cooling to room tem-
perature gave yellow-orange crystals of 5. Yield 0.81 g
(81%).
1H NMR (C6D6): 1.30 (s, 9H, OCMe3); 1.98 (s, 15H,
C5Me5). 13C {1H} NMR (C6D6): 13.34 (C5Me5); 31.68
(OCMe3); 90.50 (OCMe3); 131.05 (C5Me5). EI-MS
(50 ꢁC): m/z (relative abundance, %) 326 (MÅ+; 7), 311
([MꢀMe]+; 9), 291 ([MꢀCl]+; 2), 272 (12), 270
([MꢀC4H8]+; 18), 256 (14), 255 (23), 254 (55), 253 (36),
252 ([Mꢀt-BuOH]+; 78), 251 (9), 250 (8), 236 (12), 235
(12), 234 (27), 218 (9), 217 (16), 216 (11), 215 (9), 213
(14), 176 (8), 140 (9), 136 (11), 135 ([C5Me5]+; 100), 119
(46), 105 (38), 91 (29). IR (hexane solution, cmꢀ1): 1363
(s), 1233 (m), 1172 (s), 1065 (w), 1005 (vs), 796 (m), 758
(m), 580 (m), 479 (w), 450 (s), 406 (s).
1H NMR (C6D6): 0.45 (br s, 3H, MeB); 1.01 (s, 18H,
OCMe3); 1.63 (s, 15H, C5Me5). 13C {1H} NMR (C6D6):
12.17 (C5Me5); 31.59 (OCMe3); 90.18 (OCMe3); 130.71
1
(C5Me5); 137.44 (d of multiplets, JCF = 246 Hz, m-CF);
1
139.79 (d of multiplets, JCF = 242 Hz, p-CF); 148.87 (d
1
of multiplets, JCF = 235 Hz, o-CF); BMe and BCipso were
not observed. 19F (C6D6): ꢀ132.85 (m, 6F, o-F); ꢀ160.45
1
(m, 3F, p-F); ꢀ165.45 (br s, 2F, m-F). H NMR (CD2Cl2):
0.39 (br s, 3H, MeB); 1.35 (s, 18H, OCMe3); 2.13 (s, 15H,
C5Me5). selected 13C {1H} NMR (CD2Cl2): 13.09 (C5Me5);
32.34 (OCMe3); 129.54 (C5Me5)19F (CD2Cl2): ꢀ133.50 (m,
6F, o-F); ꢀ161.34 (m, 3F, p-F); ꢀ167.47 (br s, 6F, m-F). EI-
MS (300 ꢁC): m/z (relative abundance, %) 856 (MÅ+; not
observed), 512 ([B(C6F5)3]+Å; 14), 364 ([BF(C6F5)2]+, 16),
258 (7), 227 (10), 216 ([BF2(C6F5)]+, 17), 197 (11), 136
(32), 135 ([C5Me5]+; 100), 134 (29), 133 (20), 121 (29),
119 (56). IR (KBr, cmꢀ1): 2982 (w), 2938 (vw), 2870
(vw), 1642 (w), 1514 (s), 1460 (vs), 1381 (w), 1365 (w),
1280 (w), 1269 (w), 1174 (m), 1160 (m), 1099 (s), 1090 (s),
1006 (s), 974 (vs), 912 (vw), 895 (w), 876 (vw), 798 (m),
770 (vw), 758 (w), 747 (vw), 730 (w), 668 (vw), 654 (vw),
627 (vw), 570 (vw), 492 (vw), 433 (vw).
3.3. Synthesis of permethylcyclopentadienyl(methyl)tita-
nium tert-butanolates
3.3.1. [(g5-C5Me5)Ti(Ot-Bu)2Me] (3)
Cold diethylether solution of LiMe (1.6 M, 4.5 ml,
7.2 mmol) was dropwise added to a stirred solution of 1
(2.64 g, 7.2 mmol) in 25 ml of toluene precooled to ꢀ60 ꢁC.
The reaction mixture was allowed warming to ꢀ40 ꢁC, stir-
red for 1 h at this temperature, and degassed in vacuum.
After warming to ambient temperature the mixture was left
standing for 5 h in dark. Volatiles were evaporated in vac-
uum, and an oily residue was extracted in hexane. Pure 3
was obtained after distillation at 75 ꢁC/0.1 mm Hg as a yel-
lowish oily liquid of 3. Yield 2.34 g (94%).
3.5. NMR scale synthesis of [(g5-C5Me5)Ti
(Ot-Bu)2][B(C6F5)4] (6)
1H NMR (C6D6): 0.50 (s, 3H, TiMe); 1.30 (s, 18H,
OCMe3); 1.94 (s, 15H, C5Me5). 13C {1H} NMR (C6D6):
11.79 (C5Me5); 32.68 (OCMe3); 37.64 (TiMe); 80.47
(OCMe3); 119.62 (C5Me5). IR (hexane solution, cmꢀ1):
1357 (s), 1228 (m), 1197 (vs), 1180 (s), 1137 (w), 1106 (w),
1065 (w), 1033 (vs), 1012 (vs), 903 (w), 790 (m), 758 (w),
694 (w), 635 (w), 604 (m), 553 (m), 502 (m), 463 (w), 415 (m).
A NMR tube was charged with [Ph3C][B(C6F5)4]
(0.0424 g, 0.046 mmol) and shortly cooled in liquid nitro-
gen. A cold solution (ꢀ78 ꢁC) of 3 (0.0160 g, 0.046 mmol)
in 1.0 ml of CD2Cl2 was slowly dropped to the precooled
solid borate. The tube was immediately cooled by liquid
nitrogen, degassed in vacuum, sealed and stored in liquid
nitrogen, then placed in the NMR probe at 223 K where
3.3.2. [(g5-C5Me5)Ti(Ot-Bu)Me2] (4)
The above described protocol for 3 was used starting
from LiMe solution (1.6 M, 9.8 ml, 15.6 mmol) and 2
(2.55 g, 7.8 mmol). Crude product was extracted in hexane
it was examined for H, 13C, and 19F nuclei.
1
1H NMR (CD2Cl2, 223 K): 1.40 (s, 18H, OCMe3); 2.18
(s, 15H, C5Me5). Selected 13C {1H} NMR (CD2Cl2,
223 K): 13.09 (C5Me5); 32.06 (OCMe3); 88.98 (OCMe3);

J. Pinkas et al. / Journal of Organometallic Chemistry 692 (2007) 2064–2070
2069
129.52 (C5Me5). 19F (CD2Cl2, 223 K): ꢀ133.8 (m, 6F, o-F);
4. Supplementary material
ꢀ163.4 (m, 3F, p-F); ꢀ167.3 (m, 6F, m-F).
Note. The stoichiometric amount of the formed MeCPh3
was also observed (1H NMR (CD2Cl2, 223 K): 2.14 (s, 3H,
MeC); 7.01–7.08 (m, 6H, CHortho, Ph); 7.15–7.28 (m, 9H,
CHmeta and CHpara, Ph).)
CCDC 624680 contain the supplementary crystallo-
graphic data for 5. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
3.6. Attempted ethene polymerization with 5
In a high vacuum system a magnetically stirred satu-
rated solution of 5 in toluene (10.0 ml) was exposed to gas-
eous ethene at the pressure of 730 Torr. After the solution
was saturated with ethene, no further consumption of eth-
ene was observed. The yellow color of the solution did not
change during admission of ethene and for the next one
hour. After addition of 20 ml of methanol no polymer
precipitated.
Acknowledgements
This research was supported by Grant Agency of the
Czech Republic (Grant No. KJB4040403). V.V. was finan-
cially supported by the Ministry of Industry and Trade of
the Czech Republic (Project No. FT-TA3/078).
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